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A-Level Biology > Genetics > Flashcards

Genetics Flashcards

1
Q

Describe eukaryotic DNA

A

Large/long
Associated with histones
Found in linear chromosomes
Contained within the nucleus

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2
Q

Describe prokaryotic DNA

A

Shorter/single stranded
Not associated with histones
Single, circular loop
Free-floating in the cytoplasm

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3
Q

What is the genetic code?

A

Triplet code
Non-overlapping
Universal

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4
Q

What does it mean that the genetic code is a triplet code?

A

Every 3 bases forms a codon and one codon = one amino acid

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5
Q

What does it mean that the genetic code is non-overlapping?

A

It reads a sequence and separates it into 3s

123456 = 123, 456, 789 not 123, 234, 456

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6
Q

What does it mean that the genetic code is universal?

A

Each triplet code always codes for the dame amino acid

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7
Q

How many possible triplets is there?

A

64

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8
Q

How many different amino acids is there?

A

20

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9
Q

What does it mean that the code s.is degenerate?

A

Some amino acids are coded by more than one base

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10
Q

Do all triplet codes result in an amino acid?

A

No some act as start and stop codons

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11
Q

Describe the process of transcription

A

DNA helicase breaks H bonds
Free floating RNA nucleotides find complementary base pairs
RNA polymerase forms phosphodiester bonds between each mRNA nucleotide to form pre-mRNA

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12
Q

What is removed in splicing?

A

Introns

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13
Q

What are exons joined to form?

A

mRNA

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14
Q

What must be removed before mRNA leaves the nucleus?

A

Non-coding pieces of mRNA (introns)

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15
Q

What is translation?

A

The process by which mRNA is used to make a specific polypeptide

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16
Q

Describe the process of translation

A

mRNA moves out of the nucleus via nuclear pores
mRNA attaches to ribosome
Anti-codon forms temp H bonds with complementary bases on mRNA
Peptide bond forms between amino acids

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17
Q

When does the process of translation stop?

A

When a stop codon is reached

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18
Q

What will the other ribosomes that pass along the mRNA produce?

A

An identical polypeptide

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19
Q

What does tRNA do?

A

Transport specific amino acids

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20
Q

How many different types of tRNA is there?

A

20

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21
Q

What do all the different tRNA have in common?

A

The same structure

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22
Q

What is the structure of tRNA?

A 
Bases folded to form a clover structure
Attachment site for amino acids
Anti-codon
Base pairing
Consists of a single polynucleotide strand of RNA
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23
Q

What is a mutation?

A

Any change in one or more nucleotide base or a change in the sequence of bases in DNA

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24
Q

What are mutations?

A

Random
Spontaneous
Natural

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25
What are the three types of mutations?
Deletion Insertion Substitution
26
What is deletion?
A nucleotide is lost from the sequence
27
What is insertion?
A nucleotide is added to the sequence
28
What is substitution?
A nucleotide is replaced by another nucleotide with a different base
29
Which mutation will have the biggest impact and why?
Deletion and insertion as it will cause a frame shift (all amino acids effected)
30
Why will substitution have minimum impact?
As it will only effect one amino acid or non if it is degenerate
31
What are the two types of chromosomal mutation?
Polyploidy | Non-disjunction
32
What is polyploidy?
When organisms have three or more sets of chromosomes
33
What is non-disjunction?
When chromosomes fail to separate during meiosis
34
Which organism does polyploidy mostly occur in?
Plants
35
What is the role of mitosis meiosis in the animal body?
Growth and repair - MI | Production of gametes - ME
36
How many cell divisions is there in mitosis and meiosis?
1 - MI | 2 - ME
37
How many daughter cells are produced in mitosis and meiosis?
2 - MI | 4 - ME
38
What is the genetic composition of the daughter cells in mitosis and meiosis?
Diploid - MI | Haploid - ME
39
What is the similarity of the daughter cells to the parent cells in mitosis and meiosis?
Identical - MI | Similar but not identical - ME
40
What is meiosis?
The process by which a diploid nucleus divides to produce four haploid nuclei
41
What are the two forms of genetic variation during meiosis?
``` Crossing over (exchange of alleles) Independent segregation (Random arrangement of homologous chromosomes) ```
42
Describe meiosis
DNA unravels and replicates so there are two copies of each (chromatids) DNA condenses to form double armed chromosomes formed by two sister chromatids Joined by a centromere Meiosis 1- chromosomes arrange themselves into homologous pairs These are separated + halved Meiosis 2- Sister chromatids are separated + centromere divided 4 genetically different haploid cells produced
43
What is genetic diversity?
The total number of different alleles in a population
44
What does it mean if there is greater genetic diversity in a population?
More likely organisms are going to be suited to their environment
45
What is phenotype?
Observable physical characteristics an organism has
46
What is genotype?
Genetic makeup of an organism
47
What is the gene pool?
The total number of alleles in a population at a specific time
48
What is allele frequency?
The number of times an allele occurs within the gene pool
49
What is a normal distribution curve look like?
Data surrounds a central point Curve is symmetrical Curve is bell shaped
50
What are most characteristics a result of?
Multiple genes (polygenes)
51
What are polygenes effected by?
The environment
52
If the environment changes what part of the distribution curve changes?
The mean
53
What is selection?
The process by which organisms that are better adapted to their environment tend to survive and breed at the expense of those less well adapted
54
What are the two types of selection?
Directional | Stabilising
55
Describe directional selection (on a distribution curve)
Extreme phenotypes are favoured Changes in characteristics Shifts left and right
56
What is an example of directional selection?
Peppered moth
57
Describe stabilising selection (on a distribution curve)
Mean phenotype favoured No.of individuals with mean phenotype increases Narrower + higher but no change in mean
58
What is an example of stabilising selection?
Birth mass
59
Explain directional selection
``` Mutations = increased diversity Changes in environment Selection favours individuals that vary on one direction from the mean Mean characteristic changes Extreme phenotype is selected ```
60
Explain stabilising selection
No change in environment Extreme characteristics = less frequent No.of individuals with trait increases Mean phenotype favoured
61
What is natural selection?
The process by which organisms that are better adapted to their environment tend to survive and breed at the expense of those less well adapted
62
What is a species capable of?
Breeding to produce living, fertile offspring
63
What system is used to identify organisms?
Binomial system
64
What two taxons are used to name an organism?
Genus and species
65
What does natural selection result in?
Adaptions in organisms that are better suited to their environment
66
What are the adaptions?
Anatomical Physiological Behavioural
67
What are courtship displays important for?
Organisms don't live forever Need DNA to be passed on Occurs through reproduction Increased likelihood of reproduction
68
What are courtship displays?
A set of behaviours in which an animal attempts to attract a mate and exhibit their desire to copulate
69
What do courtship displays include?
Vocalisation Displays of beauty or strength Ritualised movements
70
Why are courtship displays important?
Enables member to recognise own species Identify a mate that is capable of breeding Form pair bonds Synchronise mating season
71
Describe a stimulus response
``` Male communicates courtship signal Acts as visual response Female nervous system detects + responds with specific behaviour Stimulus to male Male responds ```
72
What does pair bonds lead to?
Successful breeding + successful raising of offspring
73
What does synchronised mating seasons ensure?
Maximum chance of fertilisation
74
Why is it important for member to recognise their own species?
Prevent cross breeding + infertile offspring
75
Why is it important for a mate to identify a mate capable of breeding
Since both need to be sexually mature, fertile and receptive
76
What is classification?
The organisation of living organisms into groups
77
What is taxonomy?
The theory and practice of biological classifications
78
What principles are classification based on?
Artificial | Phylogenetic
79
Describe artificial classification
Based on analogous characteristics | Not based on evolutionary relationships
80
Describe phylogenetic classification
Based on homologous charcteristics | Based on evolutionary relationships
81
What is an example of artificial classification?
Colour of flower
82
What is an example of phylogenetic classification?
Limbs in animals (whether wings, arms, fins or legs) have similar structure
83
What do phylogenetics arrange animals in?
Hierarchy
84
What are the features of a phylogenetic tree?
Small groups within larger groups Taxons Based on evolutionary relationships
85
What is the order for the phylogenetic tree?
``` Life Domain Kingdom Phylum Class Order Family Genus Species ```
86
What is the most specific group?
Species
87
What are analogous structures?
They have the same function but different ancestors
88
What are the three domains?
Bacteria Eukarya Archea
89
Describe bacteria (domain)
``` No membrane bound organelles Unicellular Cell wall = murein 70s ribosomes DNA = single loop of nucleic acid not assiociated with hsitones ```
90
Describe eukarya (domain)
Membrane bound organelles Not all posses cell walls 80s ribosomes DNA = associated with histones
91
Describe archea (domain)
``` Single celled prokaryotes Similar size + shape to bacteria Genes + protein synthesis similar to eukarya Cell wall = no murein More complex form of RNA polymerase ```
92
What are the positives of just using observable characteristics?
Any one can classify an organism Cheap Easy to observe
93
What are the negatives of just using observable characteristics?
May be a result of similar environment not similar evolutionary history Pattern of inheritance is not always clear Interpretation is subjective Most genes are polygenetic
94
What does modern classification compare?
Sequence of DNA Sequence of mRNA Amino acid sequence in proteins
95
What are the disadvantages of using DNA and amino acid sequence in modern classification?
Expensive Takes a long time Some DNA is non-coding/non functional
96
What does a DNA sequence determine in modern classification?
Exact order of nucleotides | How diverse an organism is
97
What does amino acid sequence determine?
Order of DNA and mRNA
98
What does it mean if amino acid sequences are similar in modern classification?
Species are similar
99
Describe DNA hybridisation
Heat to break H bonds Combine single strands of DNA Cool to allow renaturation of double stranded DNA Determine degree of hybridisation
100
What does complete hybridisation mean?
Organisms identical
101
What does partial hybridisation mean?
Organisms related
102
What does no hybridisation mean?
Organisms aren't related
103
What does more hydrogen bonds reformed mean?
More related
104
What does a higher temp mean?
Greater no. of H bonds formed Greater similarity in DNA Closer related they are
105
Describe how immunology is used in genetics
Serum is injected into another species Rabbits produce anti-human antibodies They're mixed with serum from another species More similar species = more antibody-antigen complexes formed Precipitate formed
106
What does the larger amount of precipitate formed mean?
Closer evolutionary relationship
107
What is species diversity?
The no.of different species and the no.of individuals of each species within any one community
108
What is genetic diversity?
The variety of genes possessed by the individuals that make up one species
109
What is ecosystem diversity?
The range of different habitats within a particular area
110
If the diversity is higher what does that mean?
The more stable an ecosystem is since less of an impact an environmental change will have
111
What will happen to an ecosystem with low diversity if there is an environmental change?
It will have a high degree of change
112
What is biodiversity reduced by?
Agriculture used land for homes + industry Deforestation Production of fossil fuels
113
Why does agriculture reduce biodiversity?
Mono-culture = reduction in species Using pesticides/fertilisers = enters water cycle + leads to eutrophication Draining wetlands/marshes = removes habitats + nutrients and moisture from soil Removing hedgerows = removing habitats
114
What is deforestation?
The permanent clearing of forests and the conversion of land to other uses such as agriculture, grazing and settlement
115
Why does deforestation reduce biodiversity?
Loss of species directly | Loss of habitats
116
What are the two types of variation of species?
Intraspecific | Interspecific
117
What is intraspecific variation?
Variation within a species
118
What is interspecific variation?
Variation between species
119
What are the two quantitative methods?
Quadrats | Transects
120
What is the problem with these methods?
Unreliable Untrustworthy Unrepresentative
121
How can you make it more reliable?
By taking multiple readings to find a mean
122
How can you make it trustworthy?
Use random sampling
123
Describe sampling bias
Choice made by the investigator Sample is unrepresentative Deliberate/unwilling
124
How can sampling bias be avoided?
Random sampling
125
Describe chance variation
Not representative sample | All individuals the same
126
How can chance variation be avoided?
Increasing sample size
127
What is standard deviation a measure of?
How much the data deviates from the mean
128
What does SD enable you to do?
Improve the reliability of your results
129
What does it mean if the SD is closer to the mean value?
More probable that your results are correct
130
How do you find SD on a graph?
Measure the width of the curve | Where the graph goes from convex to concave

A-Level Biology (21 decks)

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